The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In general, an aircraft is moved by several turbojet engines each housed in a nacelle accommodating a set of auxiliary actuating devices relating to its operation and providing various functions when the turbojet engine is in operation or shut-down.
In particular, these auxiliary actuating devices comprise a thrust reverser system.
In general, a turbojet engine nacelle presents a substantially tubular structure comprising an air inlet upstream of the turbojet engine, a mid-section intended to surround a fan of said turbojet engine, a downstream section intended to surround the combustion chamber of the turbojet engine and possibly integrating thrust reversal means, and is generally terminated by an ejection nozzle whose outlet is located downstream of the turbojet engine.
Modern nacelles are intended to accommodate a bypass turbojet engine capable of generating via the blades of the rotating fan a hot air flow (primary flow) and a cold air flow (secondary flow) which circulates outside the turbojet engine through an annular passage, also called flow path, formed between a fairing of the turbojet engine and an inner wall of the nacelle. The two air flows are ejected from the turbojet engine from the rear of the nacelle.
In general, the downstream section of a nacelle for such a turbojet engine has an Outer Fixed Structure (OFS) and a concentric Inner Fixed Structure (IFS) surrounding a downstream section of the turbojet engine accommodating the gas generator of the turbojet engine.
The inner and outer fixed structures define the flow path intended to channel the cold air flow which circulates outside the turbojet engine.
The role of a thrust reverser, during the landing of an aircraft, is to improve the braking capability of said aircraft by redirecting forwards at least one portion of the air ejected from the turbojet engine. In this phase, the thrust reverser obstructs at least one portion of the flow path of the cold flow and directs this flow forwardly of the nacelle, thereby generating a counter-thrust which is added to the braking of the wheels and air brakes of the aircraft.
In general, the structure of a thrust reverser comprises a cowl which is mounted movable in longitudinal translation from forth to back along a direction substantially parallel to the axis of the nacelle, between a closure position in which the cowl provides the aerodynamic continuity of the nacelle, and an opening position in which the cowl opens a passage in the nacelle.
In the case of a thrust reverser with cascade vanes, the reorientation of the air flow is performed by cascade vanes, associated to reversal flaps blocking at least partially the air flow path, the cowl having a simple sliding function aiming to uncover or cover these cascade vanes.
In turn, the reversal flaps, also called blocking flaps, are activated and driven by sliding of the movable cowl until obstructing at least partially the flow path downstream of the cascades, so as to improve the reorientation of the cold air flow.
There are known nacelles called “O-Duct” nacelles which have a downstream structure having one single substantially peripheral structure extending from one side of the reactor mast up to the other side.
It follows that such a structure generally has one single substantially peripheral cowl which is opened, for maintenance purposes, by downstream translation along the longitudinal axis of the nacelle.
For a detailed description, reference may be made to the documents FR 2 911 372 and FR 2 952 681.
The reactor mast is a means for linking the propulsion unit to the wing of the aircraft, which carries the turbojet engine by front and rear suspensions.
There is known a mast called a “fan casing”-type mast, which includes a front portion fastened on the fan casing of the turbojet engine, in contrast with a mast called a “core”-type mast which is fastened on the core of the turbojet engine, that is to say downstream of the fan casing, for example on the hub of the fan casing or on the hub of the high-pressure compressor of the turbojet engine.
Moreover, the O-Duct nacelles include cascade vanes which are mounted movable in translation and capable of being retracted at least partially through the mid-section of the nacelle and thus overlap the fan casing when the thrust reverser is inactive, in the direct jet position. In the thrust reversal position, the cascade vanes are displaced with the movable cowl.
In the case of a thrust reverser for an O-Duct nacelle, the mast may be equipped with rails allowing the sliding of the movable cowl and of the cascades.
On modern propulsion assemblies, large-sized and having very flexible structures, this configuration may induce considerable stresses in the structure of the thrust reverser.
There is also known a thrust reverser device described in the document FR-A-3002785, which includes rails which are arranged on either side of the mast and which provides the sliding of the movable cowl and of the cascade vanes.
This type of devices has drawbacks in particular in the event of a relative displacement of the turbojet engine relative to the mast, the movable cascades, which are fastened on the mast, might be subjected to distortion forces.
Indeed, in order to limit the volume of modern nacelles, in particular the radial section of the nacelles, the section of the movable cascades is limited in order to reduce their bulk, so that the inertia of the cascades and the mechanical resistance opposed thereby is reduced.
Furthermore, there is also a risk of relative displacement of the rails relative to each other and significant geometric variations which might compromise the proper operation of the kinematics of the thrust reverser.
Finally, the mounting/dismounting of the propulsion unit implies dismounting all or part of the thrust reverser.
Furthermore, the thrust reverser device described in the document FR-A-3002785 is not adapted to a previously described “core”-type mast.
Indeed, the core-type mast has the particularity of including a longitudinal front portion inclined towards the axis of the nacelle so as to be fastened on the core of the turbojet engine.